Conventionally, well conduits were cemented into place in the wellbore. However, the use of cement is sometimes not desirable because it may reduce or interfere with the production of the well. With the introduction of non-cemented wells, open hole packers came into use. Initially, the packer designs were mechanical in nature, and, eventually, swellable packers were introduced.
Swellable packers were initially designed to swell when exposed to oil-based fluids. More recently, swellable packers that swell in the presence of water-based fluids (e.g., brine) are also in use. However, these swellable packers have drawbacks because the rubber composition is not always acceptable for use in wells and/or the rubber does not sufficiently swell when it contacts saline formation water. Moreover, it is oftentimes necessary to swell the packer as soon as possible during well operations. If the swell rate of the packer is too slow, the well operations will be delayed, which can be extremely costly to the well operator. Accordingly, there is a need for swellable packers that have sufficient swell rates and hold at high pressures in downhole conditions (for example, saline environment, high temperatures).
Granular super absorbent polymers (SAP) have been used in the art to produce swellable packers because granular SAP achieves high volume swell at high temperature. The granular SAP particles are less expensive and swell faster than non-granular SAP particles. It is oftentimes believed that larger SAP particles are better because the larger particles lead to faster swell rates and larger swell area as compared to smaller/non-granular SAP particles. However, surprisingly it was found that high levels of leaching associated with large SAP particles not only reduce the swell potential of these compounds, but the leaching creates large perforations in the rubber. These perforations produce weak points which will lead to failure when the rubber is stressed. An analogy for this would be perforated paper which when stressed will split at the perforation line.
In addition, elastomer compositions may be more difficult to process where higher amounts of granular SAPs are mixed into the composition. For example, the higher level of granular SAP may result in an unacceptable level of mixing, and the granular SAP may not be properly incorporated into the composition. In short, there is a desire to have higher loads of SAPs in the swellable packer, but not at the expense of deterioration of the other physical and/or chemical properties of the packer or the processing of elastomeric composition used for forming the swellable packer.
The present disclosure is directed to producing a swellable elastomeric composition with higher loads of SAPs wherein the composition has acceptable physical and/or chemical properties during processing, after forming and/or curing of the swellable packer, as well as when it is placed into use.
It has been unexpectedly found that by using powder SAPs, higher loads of powder SAPs may be incorporated into the elastomeric composition (as compared to loading with granular SAPs), and that the swellable composition has acceptable physical and/or chemical properties during processing, after forming and/or curing of the swellable packers, as well as when it is placed into use in the wellbore.
It has also been unexpectedly found, as disclosed herein, that higher loads of powder SAPs in the elastomeric composition result in packers with excellent swell rates in brines, low leaching and acceptable physical and/or chemical properties when subjected to the high temperature and/or high pressure conditions that occur in a wellbore.
The present disclosure is directed to elastomeric compositions and swellable packers that achieve a predictable and suitable swell rate (swelling as a function of time) such that the packer may be subjected to higher pressure in a timelier manner.
The present disclosure is also directed to swellable packers that have acceptable physical and/or chemical properties when subjected to brine type conditions, higher temperature conditions, and/or higher pressure conditions, such as those, for example, that may occur in a wellbore.
The present disclosure is directed to swellable compositions, and the packers produced using such swellable compositions, that swell at a suitable predictable rate and amount and are able to withstand high pressures and high temperatures without substantial physical failures, such as tearing and/or perforation.
Accordingly, it is desirable to have a swellable composition that is more acceptable for use with oil and gas field equipment, including, for example, a swellable packer.